Technical Field
The present disclosure generally relates to electronic circuits and, more specifically, to integrated circuits generating non-deterministic random numbers, commonly called “truly random”.
Description of the Related Art
In many electronic circuits, so-called random number generators are used. Actually, such generators generate unpredictable binary numbers, the randomness of the generated numbers being only statistical.
There exist many methods for verifying the randomness of a number generated by an electronic circuit. Such methods comprise among others performing a plurality of draws or generations of random numbers and statistically verifying the uniformity of the distribution of the generated bits. For example, for a number over one bit, the proportions of generated 1s and 0s should among others be close to each other.
For certain applications, particularly cryptographic applications, the non-deterministic character of the generated numbers or randomness is important.
A known method comprises using metastable oscillations which appear in a ring formed of an even number of logic inverting gates. This phenomenon occurs when gates of the ring are forced to certain values and are then released. The electronic noise phenomena impacting the delay of each of these logic gates result in a random variation over time of the number of oscillations before stabilization thereof. Although, theoretically, such a solution is attractive, an issue lies, on manufacturing of circuits in large series, in the guarantee of the randomness of the generated numbers. Indeed, a poor imbalance of the delay elements prevents the circuit from generating unpredictable numbers. Further, such an imbalance cannot be well controlled during the design and the manufacturing of circuits.